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COUNTING POPULATIONS

0. COUNTING POPULATIONS. How many are there?. Organism- Any living thing. Ecosystem. Collection of all the organisms in an area AND the non-living parts of the environment. 0. Population. The total number of one species living in a defined region. 0. Community.

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COUNTING POPULATIONS

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  1. 0 COUNTING POPULATIONS How many are there?

  2. Organism-Any living thing

  3. Ecosystem • Collection of all the organisms in an area AND the non-living parts of the environment

  4. 0 Population • The total number of one species living in a defined region

  5. 0 Community • Several populations in the same area that interact with each other

  6. 0 What are the 3 biggest populations in this pond community?

  7. 0

  8. How big is each population? • How can we figure out how many individuals are in each population? • A census is a count of a population

  9. Census • True census – actual count • Sample census – estimate of population • A sample census is made by marking off small areas or plots and counting in the areas

  10. 0 What are the 3 biggest populations in this pond community?

  11. 0 ACTUAL COUNT • Each member of a population is counted one by one

  12. 0 Which population was easiest to count?Which was most difficult? Why?

  13. 0 SAMPLE CENSUS • Mark off a small area or plot. • Count the population in one plot. • Multiply by the total number of plots to get an estimate for the whole area.

  14. 0 RANDOM SAMPLES

  15. 0 ACCURACY??? • Why was the last census not very accurate? • What could we do to make it more accurate? • Where have you already done a sample census?

  16. Transect-Draw a line through an ecosystem and count along it.

  17. Transect

  18. Population densityNumber of individuals that live in a unit area

  19. Population density Examples: • There are 270 people per square mile in Pennsylvania • There are 25 deer per square mile in PA

  20. 0 DISCUSSION QUESTIONS • Why is a sample a good way to count a population? • What are some disadvantages to using a sample? • What could you do to sample a population of animals that do not stay in one place?

  21. 0 MARK AND RECAPTURE • A way to count organisms that move or are hard to see. • Catch, mark, let go, catch again. • Use a formula to estimate the number.

  22. Review question • Is Mark and Recapture a true census or a sample census? • For the following animals, what method would be most appropriate for getting a census?

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